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** * Xenobiology expedition 'Profundity': Log entry 634 * **

These things are remarkably tricky to study!!

Puffer lizards live on the open salt pans of Arbslex IV (an incredibly Earthlike planet), eking out an existence by snapping up the salt flies. Mostly they’re unassuming blue grey lumps on the floor, but when any predator gets anywhere near them they leap into the air and.. well.. they puff up, floating higher and higher away from the (primarily land based) predators of the salt pans before slowly deflating and landing a safe (large) distance away. When inflated the lizards exhibit remarkable lift, shooting into the air like a helium balloon that’s had it’s string cut.

As a result of this behaviour we’ve been unable to capture a live sample for testing, and so we can’t work out how the lizards are puffing up in such a way that they generate lift. We’ve found some (very badly degraded) corpses and can confirm an exceptionally light skeleton (on the order of grams for a foot long lizard) but the organ structure is anyone’s guess.

Question for you guys at HQ is how can these lizards rapidly generate lifting gas for their escape? If we can come up with some theories the field techs can work on non lethal capture methods, but for now we’re stuck watching these little blighters floating off into the distance.

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    $\begingroup$ What's our planet look like? Earth-like? Low gravity? High density atmosphere? $\endgroup$ – bendl Apr 30 '18 at 20:58
  • $\begingroup$ @Bendl: Earthlike in all respects. Climate in the region is similar to salt pans you might find in a large desert. $\endgroup$ – Joe Bloggs Apr 30 '18 at 21:13
  • $\begingroup$ Consider your automotive airbag. Compressed into a rather small space, on command it inflates in a small fraction of a second. You just need a little chemistry to find an explosive mixture that produces H2, rather than the N2 & CO2 of most airbags. $\endgroup$ – jamesqf May 1 '18 at 5:36
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They are not puffing up. They are generating a negative pressure space within themselves.

Using photographs, the estimated volume of a puffed puffer lizard is 3 liters. Analysis of skeletal bones found the bones to be an extremely strong and light beryllium / calcium mixture, with spring loaded lever-like hinges. The lizard stores force in these springs over time and on deploying them, levers its internal puff space apart. Neither air nor any other gas flows into this space. The lizards become vacuum balloons.

Excluding air from a space of 3L would generate a lift of approximately 3.6 grams. This is not enough to lift the lizard outright but enough to make it neutrally buoyant in air, allowing it to make a prodigious jump straight up as though weighing only a few mg. Prevailing winds at height do the rest of the work. carrying the lizard along laterally as it slowly descends.

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    $\begingroup$ That would make the lizard bones and hide incredibly valuable for their mechanical properties.. nice! $\endgroup$ – Joe Bloggs May 1 '18 at 5:42
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They would need some way of quickly generating hydrogen gas; any form of compressed gas would need a strong (therefore, heavy) tissutal infrastructure to keep it compressed.

A biological holding tank for sodium hydroxide and ferrosilicon is not very much plausible, but I don't really see alternatives.

Heated air could not be easily heated enough, and it would need to be kept hot. On the other hand, it would be easier to produce - the lizard's skin might resist to the required 110-130 °C - it need not be "live" skin. Then, burping small quantities of methane gas and fresh air inside the expanded sac, and igniting it by quick strokes of flint-like teeth... it would require a very delicate, instinctive balance to avoid flaring into a grisou explosion, but it might look doable.

(However, a large net falling from a sufficient height would probably ensure a capture -- unless it made maybe the lizard explode?).

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    $\begingroup$ Exploding sky lizards. Exploding Sky Lizards...That is wonderful. $\endgroup$ – Joe Bloggs Apr 30 '18 at 21:16
  • $\begingroup$ Is sodium hydroxide/ferrosilicon exothermic? $\endgroup$ – Joe Bloggs Apr 30 '18 at 21:17
  • $\begingroup$ @JoeBloggs not per se, but you also need to add water (of course you still have the not-so-small problem of containing the sodium hydroxide!), and the NaOH-water reaction is exothermic. There's a description in the Wikipedia page for ferrosilicon. You might also try with elemental zinc and chloridric acid (another nasty customer) $\endgroup$ – LSerni Apr 30 '18 at 21:28
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    $\begingroup$ generating hydrogen gas is a good idea and doable, biology has some quite energetic reactions. Something like a bombardier beetle reaction. $\endgroup$ – John May 1 '18 at 0:08

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